revert r53268:

chrome/browser/gtk/browser_window_gtk.cc

Index: chrome/browser/gtk/browser_window_gtk.cc
diff --git a/chrome/browser/gtk/browser_window_gtk.cc b/chrome/browser/gtk/browser_window_gtk.cc
index 4d8cf72c5703b76a2e04e8787823d419505cae5e..52f70e3a77154fec0e19080af1afb1973bb8bc33 100644
--- a/chrome/browser/gtk/browser_window_gtk.cc
+++ b/chrome/browser/gtk/browser_window_gtk.cc
@@ -664,11 +664,6 @@ void BrowserWindowGtk::Close() {
   if (!window_)
     return;
 
-  // Sometimes the tabstrip will get stuck thinking it's in a drag session.
-  // Short of figuring out a repro case and actually solving the problem, this
-  // is the best way to avoid an immortal window. See http://crbug.com/23733
-  tabstrip_->CancelActiveDragSession();
-
   if (!CanClose())
     return;